The present invention relates generally to pulverized fuel ash extractors, and more particularly, to the conveyor system therein adapted to control the tension of both chains of the conveyor to prevent a slack buildup with time in either chain.
Pulverized fuel ash extractors generally embody a trough partially or wholly filled with water in which the ash is dispensed. Disposed within the trough is a conveyor of at least two chains or belts interconnected by cross members or drag bars spaced such that the ash falls between the bars to a bottom plate. The ash build up is then removed by the continuous movement of the drag bars along the bottom plate.
With the passage of time, the conveyor, or more particularly, the chains elongate due to friction throughout the system and a slack build up develops. In order to keep the chains taut, known tension devices, such as the one shown in German Pat. No. 839,473, are incorporated within the system, generally with two or more moveable sprockets, one for each chain. However, the tension devices of this type are generally mounted on a common shaft and are therefore unable to differentially adjust the tension of the chains to correct uneven elongation between the two chains. Furthermore, this common shaft may be slightly tilted, however, the tilting of the shaft tilts the sprocket wheels away from the direction of the chain. This misalignment between the sprockets and the chains results in accelerated wear of the chain, or increased elongation, as well as accelerated wear of the running surfaces of the sprockets. In addition, the chain is more likely to disengage itself from one of the tilled sprockets. Thus, an exchange of conveyors is required not only when the chains are completely worn out, but also when a significant differential elongation exists between two chains.
In the interest of efficiency and economy, it is clear that a reduction in conveyor exchange rates may be realized by a tension device which will elongate and/or differentially elongate.